Image file formats

Image File Formats

Filename extension	Various (.jpg, .png, .gif, etc.)
Magic number	Various
Initial release	Various dates

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Image file formats are standardized means of organizing and storing digital images. Image files are composed of digital data in one of these formats that can be rasterized for use on a computer display or printer. An image file format may store data in uncompressed, compressed, or vector formats. Once rasterized, an image becomes a grid of pixels, each of which has a number of bits to designate its color equal to the color depth of the device displaying it.

Types of Image File Formats

Image file formats are generally categorized into three main types: raster, vector, and compound formats.

Raster Formats

Raster image formats encode information in a grid of pixels. These formats are widely used for photographs and other types of images that require a rich color palette. Common raster formats include:

• JPEG (Joint Photographic Experts Group) - uses lossy compression.
• PNG (Portable Network Graphics) - supports lossless compression and transparency.
• GIF (Graphics Interchange Format) - supports only 256 colors and simple animations.
• BMP (Bitmap) - uncompressed and therefore large in file size.
• TIFF (Tagged Image File Format) - widely used in publishing and photography, supports both loss and lossless compression.

Vector Formats

Vector image formats store instructions for drawing the image using lines and shapes. These are resolution-independent and are ideal for graphics such as logos and illustrations. Common vector formats include:

• SVG (Scalable Vector Graphics) - used for web graphics.
• EPS (Encapsulated PostScript) - used in professional graphic arts.
• PDF (Portable Document Format) - often used for documents but can also contain vector graphics.

Compound Formats

Compound formats may contain both raster and vector data. They are useful for complex graphics. An example of a compound format is:

• PDF (Portable Document Format) - can include both raster images and vector graphics.

Usage

Different image file formats are used based on their strengths and weaknesses. For example, JPEG is often used for photographs on the web due to its balance of quality and file size. PNG is preferred for images requiring transparency or without the need for compression artifacts.

Compression

Compression can be either lossy or lossless. Lossy compression reduces file size by removing image data, which can degrade quality. Lossless compression reduces file size without affecting the quality of the image.

See also

• Digital photography
• Graphic design
• Computer graphics